1. Technical Field of the Invention
The present invention relates to electrophoretic devices, and more particularly, relates to an electrophoretic device comprising microcapsules which enclose a liquid-phase dispersion medium and electrophoretic particles and which are provided between a pair of substrates, at least one of which is formed of a transparent material, and to a manufacturing method therefor.
In addition, the present invention relates to various electronic apparatuses each provided with an electrophoretic display device incorporating the above electrophoretic device.
2. Description of the Related Art
Hitherto, concerning electrophoretic devices comprising an electrophoretic dispersion which contains a liquid-phase dispersion medium and electrophoretic particles and which is accommodated between a pair of substrates, an application of these devices to electrophoretic display devices has been known in which change in distribution of the electrophoretic particles caused by a voltage impressed to the electrophoretic dispersion is used.
In addition, among the electrophoretic display devices as described above, an electrophoretic display device has been known in which an electrophoretic dispersion is enclosed in microcapsules, and these microcapsules are accommodated between a pair of substrates. Hereinafter, the electrophoretic display device having the structure as described above is referred to as a microcapsule type electrophoretic display device.
FIG. 13(a) is a view showing the general structure of a microcapsule type electrophoretic display device. This electrophoretic display device 20 comprises an electrode 3 formed on a first substrate 1, and a transparent electrode 4 formed of a second electrode 2. Between these electrode 3 and transparent electrode 4, microcapsules 40 are accommodated together with a binder 41, whenever necessary. This figure is regarded as a cross-section of one pixel of the display device.
In each microcapsule 40, an electrophoretic dispersion 10 is enclosed which contains a liquid-phase dispersion medium 6 and electrophoretic particles 5 dispersed in this liquid-phase dispersion medium 6. In addition, it is assumed that the liquid-phase dispersion medium 6 and the electrophoretic particles 5 are colored in different colors from each other.
To this electrophoretic display device 20, voltage sources 9a and 9b, which apply voltages in the direction opposite to each other, are connected via a switch 8. That is, the electrode 3 is connected to one end of each of the voltage sources 9a and 9b, and the electrode 4 is connected to the other end of each of the voltage sources 9a and 9b via the switch 8. When electrical connection is formed as described above, by switching the switch 8, the direction of a voltage to be applied between the electrode 3 and the electrode 4 can be changed. By changing the direction of a voltage to be applied, the electrophoretic particles can be gathered at a desired electrode side, thereby performing desired display. That is, when the electrophoretic particles 5 are positively charged, as shown in (b) of the same figure, by applying a voltage of the voltage source 9a, the electrophoretic particles 5 can be gathered at the transparent electrode 4 side which is close to an observer. In the state described above, the observer can view the color of the electrophoretic particles 5. On the other hand, as shown in (c) of the same figure, by applying a voltage of the voltage source 9b, the electrophoretic particles 5 can be gathered at the electrode 3 side which is far from the observer. In the state described above, the observer views the color of the liquid-phase dispersion 6. When the electrophoretic particles 5 are negatively charged, the moving direction of the particles is opposite to that described above.
As described above, when the structure shown in FIG. 13(a) is employed, since two types of colors each corresponding to the direction of a voltage to be applied can be displayed, an electrophoretic display device can be realized when the structure shown in the same figure is applied to every pixel, and the pixels are disposed in a matrix.
By the way, in the electrophoretic display device described above, in order to achieve improvement in fineness of displayed images and to increase information amount, color display has been desired.
As means for realizing color display, for example, a method has been proposed in which dispersing media each colored in one of predetermined three primary colors and electrophoretic particles having a color different from the three primary colors mentioned above are enclosed in microcapsules, and the three types of microcapsules thus formed which can be discriminated from each other by the colors of the dispersing media are used. However, in this method, the three types of microcapsules must be regularly and precisely arranged, resulting in a problem in that the manufacturing process becomes extremely complicated.
Alternatively, a method for realizing color display by combination of color filters has also been considered. However, when this method is applied to a microcapsule type display device, due to increase in the number of constituent elements, the cost is increased, and in addition, since color filters are disposed outside of a mixed layer of the microcapsules and the binder, a problem of parallax may arise.
Accordingly, the present invention was made in order to solve the problems of the conventional techniques described above, and a first object is to provide an electrophoretic device which can be manufactured by a simple process without increase in cost, and in which parallax will not be generated.
In addition, a second object of the present invention is to provide an electronic apparatus provided with a display device, in which even when the display device is an electrophoretic display device, parallax will not be generated.
In order to solve the problems described above and to achieve the above objects, the present invention was made as described below.
An electrophoretic device of the present invention comprises: a first substrate; a first electrode provided on the first substrate; a second substrate; a second electrode which is provided on the second substrate and which opposes the first electrode; and an electrooptic layer provided between the first electrode and the second electrode; wherein microcapsules enclosing an electrophoretic dispersion, which contains a liquid-phase dispersion medium and electrophoretic particles, are accommodated in the electrooptic layer, and wall films of the microcapsules at a viewing side are colored. According to the structure described above, since color filters are not necessary to use, the cost is not increased, and since the microcapsule wall films at the viewing side, which are in contact with the electrophoretic dispersion, are colored, the generation of parallax can be avoided. In the present invention, xe2x80x9cthe viewing sidexe2x80x9d described above means one of the major surfaces of the electrophoretic device, which is viewed by an observer, and when the electrophoretic device is used as a display device, the viewing side means a displaying surface side thereof.
An electrophoretic device of the present invention comprises: a first substrate; a first electrode provided on the first substrate; a second substrate; a second electrode which is provided on the second substrate and which opposes the first electrode; and an electrooptic layer provided between the first electrode and the second electrode; wherein a binder and microcapsules enclosing an electrophoretic dispersion, which contains a liquid-phase dispersion medium and electrophoretic particles, are accommodated in the electrooptic layer, and the binder at a viewing side is colored. According to the structure described above, the same advantages as described above can be obtained. That is, according to this structure, since color filters are not necessary to be used, the cost is not increased, and since the viewing side of the binder surrounding the peripheries of the microcapsules is colored, the generation of parallax can be avoided.
In addition, an electrophoretic device of the present invention comprises: a first substrate; a first electrode provided on the first substrate; a second substrate; a second electrode which is provided on the second substrate and which opposes the first electrode; and an electrooptic layer provided between the first electrode and the second electrode; wherein a binder and microcapsules enclosing an electrophoretic dispersion, which contains a liquid-phase dispersion medium and electrophoretic particles, are accommodated in the electrooptic layer, and at least one of the binder and wall films of the microcapsules at a viewing side is colored. According to the structure described above, the same advantages as described above can be obtained. That is, according to this structure, since color filters are not necessary to be used, the cost is not increased, and since at least one of the binder and the microcapsule wall films, which are in contact with the electrophoretic dispersion, is colored, the generation of parallax can be avoided.
The electrophoretic device of the present invention may have the structure in which the wall films of the microcapsules are colored in at least two types of colors. According to the structure described above, regardless of arrangement of the microcapsules, coloration can be performed at predetermined positions.
The electrophoretic device of the present invention may have the structure in which the binder is colored in at least two types of colors. According to the structure described above, even when the binder is unevenly distributed, regardless of the state mentioned above, coloration can be performed at predetermined positions.
The electrophoretic device of the present invention may further comprise a plurality of dot areas on a surface of the substrate, wherein the electrooptic layer may have a plurality of hues, and at least one of said plurality of hues corresponds to each of the dot areas. According to the structure described above, the electrophoretic device can be provided which exhibits a different hue in each of the dot areas.
In the electrophoretic device of the present invention, the electrooptic layer may have a plurality of hues, and said plurality of hues may correspond to three primary colors of additive mixing or subtractive mixing.
According to the structure described above, a desired hue can be displayed by combination of these three primary colors.
The electrophoretic device of the present invention may have the structure in which the wall films of the microcapsules and the binder may be colored in different colors from each other. According to the structure described above, variation of colors to be displayed can be increased.
Next, a method of the present invention for manufacturing an electrophoretic device is a method for manufacturing an electrophoretic device comprising a first substrate, a first electrode provided on the first substrate, a second substrate, a second electrode which is provided on the second substrate and which opposes the first electrode, and an electrooptic layer provided between the first electrode and the second electrode, in which the microcapsules enclosing an electrophoretic dispersion, which contains a liquid-phase dispersion medium and electrophoretic particles, are accommodated in the electrooptic layer.
The method described above comprises a step of performing coloration of wall films of the microcapsules from one surface side of the electrooptic layer in which the microcapsules are accommodated. According to the structure described above, since it is not necessary that the color filters be additionally provided for color display, the electrophoretic device can be manufactured at a reasonable cost, and in addition, since it is not necessary to consider the arrangement of the microcapsules as in the method in which coloration of the wall films and the dispersion, which constitute the microcapsules, is performed beforehand, an electrophoretic display device for color display can be significantly easily manufactured.
In a method for manufacturing an electrophoretic device, the electrophoretic device comprises a first substrate, a first electrode provided on the first substrate, a second substrate, a second electrode which is provided on the second substrate and which opposes the first electrode, and an electrooptic layer provided between the first electrode and the second electrode, wherein a binder and microcapsules enclosing an electrophoretic dispersion, which contains a liquid-phase dispersion medium and electrophoretic particles, are accommodated in the electrooptic layer.
The method described above comprises a step of performing coloration of wall films of the microcapsules and/or the binder from one surface side of the electrooptic layer in which the microcapsules and the binder are accommodated. According to the structure described above, advantages equivalent to those described above can be obtained.
In the method of the present invention for manufacturing an electrophoretic device, the wall films of the microcapsules and/or the binder may be colored by a printing method. According to the structure described above, the electrophoretic device can be formed by an easy process. The printing method mentioned above may be performed by an ink-jet method, a screen printing method, an offset method, or the like.
The method of the present invention for manufacturing an electrophoretic device may further comprise a step of moving relative positions of a head for ejecting a coloring material and the substrate, and a step of ejecting the coloring material from the head to one surface side of the electrooptic layer. According to the structure described above, since the coloring material can be precisely arranged at predetermined positions, a coloration step of performing complicated coloration can be easily carried out.
Next, an electronic apparatus of the present invention is an electronic apparatus comprising a display device for displaying data, wherein the display device described above is formed of the electrophoretic display device incorporating one of the electrophoretic device described above. According to the structure of the electronic device described above, even when the display device is an electrophoretic display device, an electronic device having a display device in which parallax is not generated can be obtained.